worker: reset Isolate stack limit after entering Locker

It turns out that using `v8::Locker` undoes the effects of
passing an explicit stack limit as part of the `Isolate`’s
resource constraints.

Therefore, reset the stack limit manually after entering a Locker.

Refs: #26049 (comment)

PR-URL: #31593
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: Gus Caplan <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Rich Trott <[email protected]>

Author: addaleax

src/node_worker.cc

@@ -159,6 +159,9 @@ class WorkerThreadData {
     {
       Locker locker(isolate);
       Isolate::Scope isolate_scope(isolate);
+      // V8 computes its stack limit the first time a `Locker` is used based on
+      // --stack-size. Reset it to the correct value.
+      isolate->SetStackLimit(w->stack_base_);
 
       HandleScope handle_scope(isolate);
       isolate_data_.reset(CreateIsolateData(isolate,

test/parallel/test-worker-stack-overflow-stack-size.js

@@ -0,0 +1,43 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { once } = require('events');
+const v8 = require('v8');
+const { Worker } = require('worker_threads');
+
+// Verify that Workers don't care about --stack-size, as they have their own
+// fixed and known stack sizes.
+
+async function runWorker() {
+  const empiricalStackDepth = new Uint32Array(new SharedArrayBuffer(4));
+  const worker = new Worker(`
+  const { workerData: { empiricalStackDepth } } = require('worker_threads');
+  function f() {
+    empiricalStackDepth[0]++;
+    f();
+  }
+  f();`, {
+    eval: true,
+    workerData: { empiricalStackDepth }
+  });
+
+  const [ error ] = await once(worker, 'error');
+
+  common.expectsError({
+    constructor: RangeError,
+    message: 'Maximum call stack size exceeded'
+  })(error);
+
+  return empiricalStackDepth[0];
+}
+
+(async function() {
+  v8.setFlagsFromString('--stack-size=500');
+  const w1stack = await runWorker();
+  v8.setFlagsFromString('--stack-size=1000');
+  const w2stack = await runWorker();
+  // Make sure the two stack sizes are within 10 % of each other, i.e. not
+  // affected by the different `--stack-size` settings.
+  assert(Math.max(w1stack, w2stack) / Math.min(w1stack, w2stack) < 1.1,
+         `w1stack = ${w1stack}, w2stack ${w2stack} are too far apart`);
+})().then(common.mustCall());